Research Project

Brazing Dissimilar Metals with Novel Composite Foils

This DoE and U.S. Army project seeks to create and optimize novel reactive foils that are capable of joining dissimilar metals and alloys. Emphasis is placed on creating brazes that are mechanically and chemically robust for a variety of material combinations.

Systems whose components are made of dissimilar metals and alloys can be difficult to assemble due to differences in thermal properties, such as melting temperature. In an attempt to circumvent this issue, our group is developing thermite-based reactive foils that can deliver large amounts of heat while producing a molten braze to wet the two components being joined. This braze is the reduced metallic product of the thermite reaction, and the amount and composition is being tailored to optimize wetting and bond strength and to minimize corrosion. Figure 1 shows the result of a preliminary bonding trial.

Figure 1. Cross-section of an Al-Al interface, bonded with an Al:CuO foil.

Figure 1. Cross-section of an Al-Al interface, bonded with an Al:CuO foil.

This project seeks to create robust, chemically stable bonds between dissimilar metals and alloys using these novel reactive materials. Foils are created from mixed powder compacts, where powder size is on the order of 10s of microns in diameter. Refinement of foil microstructure is achieved through intense mechanical processing. Once ignited, the thermite foils are highly exothermic and the resulting reaction is self-propagating. We will systematically investigate the effects of chemistry, microstructure, and other parameters in order to optimize bonding between several relevant alloys. We will also characterize the reaction properties of the foils in order to gain insight into how these materials compare to reactive materials based on formation reactions.

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